I recently found a colony of feral bees in a fallen tree near some of my hives. As I looked closely at the bees around the entrance, I noticed that several had a relatively large (0.5-1 mm) blister-like bump on the thorax.
What are the most likely causes of such a deformity? Do I need to worry about my bees having been exposed?
Was this bump reddish in color? It might be varroa.
Compare it with the picture at: http://www.kohala.net/bees/varroa.html
If it is varroa, then it definately could be a problem for your hives. Bees will drift (or rob) carrying the mites to your hive.
Bingo! Thanks for the link, tarheit; that is it, exactly.
It appears that I have had my first encounter with the Dread Varroa mite. I really had no idea they were so large. I always pictured them as almost microscopic, but there was no mistaking the presence of these monsters.
The property owner has had the feral bees destroyed, so that is at least a comfort, but I will definitely keep a close eye on my hives from now on.
Thanks again for the help!
Once you see them, varroa mites aren't hard to spot, but many people have serious infestations and never see them.
Put some (2 or 3) Oxamite strips in your hive this will help a lot, many mites coming in contact with the substances from the strips and die.
I have strips in my colonies for several week and there is a continue mite fall I never had before. There must be suffering colonies in my neighborhood.
I think this is better than a sugar roll test to find out whether colonies are infected or not